The ever growing need for energy-efficient and fast communications is driving the development of highly integrated photonic circuits where controlling light at the nanoscale becomes the most critical aspect of information transfer [1]. Routing and coupling devices based on Multimode Interference (MMI) [2,3,4] and evanescent coupling [5,6] are important building blocks in these integrated photonics circuits and have been employed as optical modulators, as mode converters and switches for high speed communication [7-9], and in data processing and integrated quantum operations [10-11]. However, active control over the coupling between closely packed waveguides is highly desirable and yet remains a critical barrier towards ultra-small footprint devices. A general approach to achieve active control in waveguide systems is to exploit optical nonlinearities enabled by a strong control pulse [12-18]. However, these devices suffer from the nonlinear absorption induced by the intense control pulse as the signal and its control propagate in the same waveguide [12, 17-18].